Flanged spool for tape record carriers



March 22, 1966 F. LAA

FLANGED SPOOL FOR TAPE RECORD CARRIERS Filed Nov. 28, 1961 M W. H mm VR m R F United States Patent Ofiice 3,2411% Patented Mar. 22, 11966 3,241,783 FLANGESD SPUUL FUR TAPE RECORD (IARRIERS Friedrich Laa, Vienna, Austria, assignor to North Amencan Philips Qompany, inc, New York, N.Y., a corporation of Delaware Filed Nov. 28, 1961, Ser. No. 155,440 Claims priority, application Austria, Dec. 2, 1960, A 2018/60 4 Claims. (Cl. 24274) The invention relates to a flanged spool for a tapeshaped record carrier, in which the flanges comprise recesses which are cut through the flanges at right angles and extend from the edges of the flanges into the spool core at an oblique angle.

if in such a spool an extension provided at the beginning of the tape, and extending on both sides beyond the width of the tape, is introduced into the mouth of the recess in approximately radial direction and if the spool is then rotated, in the direction which is determined by the direction of the sides of the recesses extending from the spool core outwards at an oblique angle, the extension of the tape will be caught by the sides located behind it in the direction of rotation and conducted to the core of the spool to be retained there. When using such spools and tapes, no particular manipulations are required to secure the tape to the core of the spool. After introducing it into a recess, this is carried out automatically. Devices have already been proposed in which also the introduction of the extension into the recesses is effected automatically.

At first sight it seems that no difliculties can present themselves in unwinding a supply of tape wound on such a spool in a manner such that, when unwinding, the tape pulls the spool and rotates it. One is apt to assume that the extension, after unwinding the last turn from the tape, simply looses its hold on the core which unwinding is continued and then, following the direction of tension in the tape extending tangentially at the circumference of the core in the direction of the flange edges defining the recesses, leaves the recesses outwards. Actually, however, in particular if the tape is unwound at high speed, for example in the case of a fast forward movement or backward movement in magnetic recorders, the extension gets easily entangled at the sides of the recesses before it leaves these recesses and jerky strains occur at the tape which may result in breakages of the tape. When using such spools in devices in which the extension is automatically introduced into the recesses, the extension is jammed and operation of the recorder is entirely disturbed in this manner.

Extensive investigations have proved that all disturbances can be avoided by a particular construction of the sides of the recesses of the spool flange. According to the invention, the side of the recess from the spool core to the edge of the flange co-operating with the tape extension on winding is varied substantially according to an involute. As a result of this when unwinding a supply of tape from a spool driven by the tape at constant linear speed, an entirely free travel which is not disturbed by the edges of the recesses is ensured for the extension leaving the core in a tangential direction. The determination of the variation of this side of the recesses may be effected, for example, on the basis of the average obliqueness of the side of the recesses as well as on the proportions of the spool core and the extension which will be explained below.

if a tape is to be automatically wound on spools to which the invention relates, the sides of the recesses,

viewed from the spool core towards the flange edges, should point in the direction of rotation of the spool for catching the extension. When unwinding, the sides conse quently point away from the direction of rotation. As such, all the points on a rotating spool have the same angular velocity. With increasing distance from the centre, the linear speed consequently increases. If a point is viewed on a rotating spool which moves on the sides of a recess of the spool from the core to the outside, an additional tangential component of the linear speed is established which is greater as the edges are more oblique.

FIG. 1 of the drawing illustrating the subject invention is an enlarged, partial view of the spool shown in FIG. 2. In FIG. 1 a tape leader is also shown for purposes of description.

PEG. 2 is a full view of the spool omitting the leader.

Referring to the drawing, the side flanges F, attached to a core K, are recessed at D for receiving a cylindrical tape leader or attachment A. The leader A is drawn toward the center of the spool by sliding on the surface iii of the side flanges when the spool is rotated in a clockwise or take-up direction.

When the spool is rotated counterclockwise, for unwinding a tape coiled on the spool at high speed, the involute shape of surface 10 (which is leading the leader A) allows the leader to be freely discharged from the recess without obstruction as indicated by the phantom lines of FIG. 1.

The spool is rotated in the unwinding direction when the tape attached to the leader is pulled in the direction T The involute shape of surface 10 defining part of the recesses in each flange of the spool is somewhat unfavorable for drawing the leader to the core of spool during takeup, however, the involute shape of the surface it) is most necessary for high speed unwinding of the spool without breaking the tape when the leader is ejected from the spool recess. The take-up function of the surface 10 is improved by increasing the radius of the flange somewhat to provide a projection V.

What is claimed is:

1. A spool for tape recorders comprising a core memher having opposed side flanges attached thereto, a pair of non-parallel involute surfaces in each said flange diverging outwardly from said core to the periphery of each said flange, said surfaces defining oblique co-axial recesses in each said flange whereby a film extension is freely ejected from said recesses upon rotation of said spool in a given direction.

2. A spool for tape recorders comprising a core member having opposed side flanges attached thereto, a pair of non-parallel surfaces in each said flange diverging outwardly from said core to the periphery of each said flange, for defining oblique coaxial recesses in each said flange, the surface in each said flange leading during unwinding rotation of said spool defining an involute curve whereby a film extension is freely ejected from said recesses during unwinding rotation of said spool.

3. A spool for tape recorders comprising a core member having opposed side flanges attached thereto, a pair of non-parallel curvilinear surfaces in each said flange diverging outwardly to the periphery of each said flange, said surfaces defining oblique coaxial recesses in each said flange, the surface of said recess leading during unwinding rotation of said spool defining an involute curve and the surface of said recess trailing during unwinding rotation of said spool being displaced in the direction opposite the direction of rotation of said spool during unwinda ing a distance greater than the distance defined by an involute trailing surface of said recess, and a protrusion extending radially outwardly of said flange adjacent said leading surface.

4. A spool for tape recorders comprising a core member having opposed side flanges attached thereto, a pair of non-parallel surfaces in each said flange diverging outwardly from said core to the periphery of each said flange, the surface in each said flange leading during unwinding rotation of said spool defining an involute curve over a substantial portion of its length, said portion extending outwardly from said core in the direction of the periphery of said flanges, said surfaces defining oblique coaxial recesses in each said flange whereby a film extension trail- 4- References Cited by the Examiner UNITED STATES PATENTS MERVIN STEIN, Primary Examiner.

H. R. MASELEY, I. P. STRIZAK, RUSSELL C.

MADER, DONALD W. PARKER, Examiners.

ing said involute surface during unwinding rotation of 15 I. C. GARVIN, O. M. SIMPSON, N. L. MINTZ, G. F.

said spool is freely ejected from said recesses.

MAUTZ, Assistant Examiners. 

1. A SPOOL FOR TAPE RECORDERS COMPRISING A CORE MEMBER HAVING OPPOSED SIDE FLANGES ATTACHED THERETO, A PAIR OF NON-PARALLEL INVOLUTE SURFACES IN EACH SAID FLANGE DIVERGING OUTWARDLY FROM SAID CORE TO THE PERIPHERY OF EACH SAID FLANGE, SAID SURFACE DEFINING OBLIQUE CO-AXIAL RECESSES IN EACH SAID FLANGE WHEREBY A FILM EXTENSION IS FREELY EJECTED FROM SAID RECESSES UPON ROTATION OF SAID SPOOL IN A GIVEN DIRECTION. 